This disclosure pertains to optical imagers in general and in particular to a dual field of view refractive optical system for geosynchronous earth orbit.
Demand for imaging sensors that provide wide area surveillance is increasing. Wide area surveillance can be used in various applications such as on an unmanned aerial vehicle (UAV) platform for target recognition or on satellites such as satellites on geostationary or geosynchronous earth orbit (GEO). Wide area surveillance can be performed at various wavelength ranges depending on the desired application. The wavelength ranges of interest include short wavelength infrared radiation (SWIR) in the wavelength range between approximately 1 μm and 3 μm, mid wavelength infrared radiation (MWIR) in the wavelength range between approximately 3 μm and 5 μm, and long wavelength infrared radiation (LWIR) in the wavelength range between approximately 8 μm and 12 μm.
For example, optical systems from GEO orbits are sought for missile warning. However, current optical systems use sensors such as a starring focal plane arrays (FPA) sensors that are about 4000 by about 4000 pixels provide a ground sample distance of about 3 km which is larger than desired in certain applications or for certain functions.
Current GEO acquisition sensors operate in a scanning mode using a linear array of detectors. Starring FPA sensors that have been incorporated into scanning imagers have typically very small field of views (FOV), about 1 to 2 degrees. These scanning imagers do not provide coverage of an entire region of interest. In addition, current GEO acquisition sensors require scanning to be interrupted. Indeed, scanning sensors take a longer period of time to provide a full area coverage (e.g., full earth coverage takes about 10 seconds) due to the linear motion coupled with certain inefficiencies in the scanning operation.
Hence, there is a need in the art for optical systems with a dual field of view refractive optical system for GEO orbit that allow both viewing a broader area or region of interest while being able to zoom to a desired smaller area within the broader area for a more detailed view of the smaller area.